Plastic cartridge casing

ABSTRACT

A method of making a one-piece plastic shotgun shell, i.e., where the transverse base portion is integral with the tubular body portion. A tubular plastic slug is carried progressively through a series of dies to produce a shotgun shell having a body portion which is highly oriented and a head section of somewhat lesser orientation. An oriented, integral primer gas seal skirt is formed inside the primer opening.

Unitedistates Patent [191 Eckstein et al.

PLASTIC CARTRIDGE CASING Inventors: George R. Eckstein; William G.

Moyher, both of Fairfield, Conn.

Assignee: Remington Arms Company, Inc.,

Bridgeport, Conn.

Filed: Nov. 18, 1971 Appl; No.: 199,913

US. Cl l02/43 P, 102/45 Int. Cl. F42b 7/06 Field of Search.. 102/38, 42R, 43 R, 43 P, 44,

References Cited UNITED STATES PATENTS 10/1971 Herter et a1. 102/43 PJan. 22, 1974 3,185,095 5/1965 Mayer et al [02/44 3,370,534 2/1968Herter 102/43 P 3,514,468 5/1970 Sutcliffe et al. 102/43 P 2,668,3452/1954 Eckstein 102/43 R Primary Examiner-Stephen C. Bentley Attorney,Agent, or Firm-John H. Lewis, Jr. et a]' [57] ABSTRACT A method ofmaking a one-piece plastic shotgun shell, i.e., where the transversebase portion is integralwith the tubular body portion. A tubular plasticslug is carried progressively through a series of dies to produce ashotgun shell having a body portion which is highly oriented and a headsection of somewhat lesser orientation. An oriented, integral primer gasseal skirt is formed inside the primer opening.

4 Claims, 19 Drawing Figures PATENIEDJAIZZ me Ill/1 PLASTIC CARTRIDGECASING to provide the base portion of a shotgun shell including a novelprimer sealing means.

The use of biaxially oriented plastic, i.e., highdensity polyethylene,in shotgunshells, began in this country in the early 1960s as a resultof the invention claimed in the Covington et al U.-S. Pat. No. 3 ,103,170, issued Sept. 10, 1963. Today, all the major US. and

Canadian manufacturers provide plastic shells with biaxially orientedbodies. Since that time, the practice of the consumer reloading hisshotshell casings has increased substantially so that ammunition beingmanufactured today must take the reloader into consideration.

The advantages of providing a one-piece plastic shell, i. erwith baseportion integrally formed with the body portion, are well known and neednot be repeated here. One-piece shells have been known for a long time.See U S. Pat. No. 1,364,871 to Ernst dated Jan. .11, 1921; U. S..Pat.No. 2,232,634 to Roberts et al dated Feb. 18, 1941; U. S. Pat. No.2,349,970 to Lambee k dated May 30, 1944; U. S. Pat. .No. 3,171,350 toMetcalf dated Mar. 2, .1965; U. S. Pat. No. 3,284,560 to King et aldated Nov. 8, 1966; U. S. Pat. No. 3,377,951 to Larson dated Apr. 16,:1968; and French Patent No. 1,170,851 (Core) published on Jan. 20, 1959.

Some of the shells described in the patents cited above are plasticshells having integral body and base portions which were developed frominjection molded slugs, or starting pieces and which require that thetinished head and basewad portion remain in substantially as-moldedcondition, free from deformation and orientation. Unlike such shells,all portions of the tbasewad portion of the present invention undergosubstantial degrees. of cold plastic deformation with the usual resultson the physical properties of the cold-worked plastic.

The present process is an adaptation of a process originally used tomake aluminum shotshell and center fire cases. See U. S. Pat. No.2,668,345 to G. R. Ecksten issued on Feb. 9, i954. However, there aredifferences in working with plastic, some of which will be describedduring the explanation of the process below.

A particular point of novelty, in the present case, is the primer gassealing means and the method of forming the gas sealing means. There arevarious means presently in use or. proposed for use which call for gassealing rings or skirts located at the front end of the primerbore which.are in direct contact with the propellantmeans so that they are movedby the explosive combustion pressure in the shell to engage the frontend of the primer to effect gas sealing.

Aslong as these gas sealing rings remain intact, reasonable sealing ofthe explosive gases between the primer and the primer bore can beexpected. However, it the gas sealing ring becomes detached or broken,as sometimes happens when reloading a spent shell, the

gas sealing means is rendered inoperative and the shell becomes uselessfor further reloading.

Because the primer sealing ring of the present invention is found insidethe primer bore, it is protected to some degree from mis-aligneddepriming pins and thus is less susceptible to being damaged.

It is a general object of this invention to provide a cartridge ofthermoplastic material in which the tubular body portion and integralbase portion are oriented, the tubular body portion to a high degree andthe integral base portion to a substantially lesser degree. A particularobject of the invention is to provide a novel primer sealing means whichwill be effective to seal a variety of lengths and diameters of primers.

These and other objects, features, and advantages of the invention willbe more fully brought out in the following specitication, claims anddrawings in which:

FIG. 1 is a cross-sectional view of a one-piece plastic shotshell madeaccording to the present invention.

FIG. 2 is an exploded cross-sectional view of the primer opening and theassociated gas sealing ring.

FIG. 2A is the same view as FIG. 2 except that a primer means is shownin place.

FIG. 3 is a cross-sectional view of the starting plastic slug. 1

FIG. 4 is a cross-sectional view of a radially expanded slug which hasalso been flared at one end.

FIG. 5 is a cross-sectional view of the impactextruded plastic body witha thickened wall portion at one end of and on the exterior of the body.

FIG. 6 is a cross-sectional view of the extruded plastic body after theforward end is trimmed and the thickened rear end portion inverted sothat the mass of plastic is now inside the body.

FIG. 7 is a cross-sectional view of the plastic body after the thickenedrear end portion is deformed to form a cartridge base portion with aprimer opening and an extruded ring surrounding the portion of theprimer opening opposite the tubular body section.

FIG. 8 is a cross-sectional view of the plastic body of FIG. 7 aftersizing.

FIG. 9 is a cross-sectional view of the punch and die arrangement forthe preform step which results in an expanded and flared preform asshown in FIG. 4.

FIG. 10 is a cross-sectional view of the punch and die arrangement forthe impact extrusion step which results in an oriented body as shown inFIG. 5.

FIG. 11 is a schematic view of a trimming means which removes the lowerend of the body member shown in FIG. 5.

FIG. 12 is a cross-sectional view of the shrouding hunter and supportmeans of the folding or inverting step which results in the plasticcartridge casing shown in FIG. 6.

FIG. 13 is a cross-sectional view of the hunter and die means of thepre-heading step which results in the cartridge casing shown in FIG. 7.

FIG. 14 is a cross-sectional view of the plastic cartridge casing beingpushed through a sizing die.

FIG. 15 is a cross sectional view of the rearwardly extending extrudedcollar on the pre-headed plastic cartridge being impacted to form aforwardly extending annular ring which eventually becomes the primersealing ring.

FIG. 16 is a cross-sectional view of feeding the metal cap to theplastic shell.

FIG. 17 is a cross-sectional view showing the first heading bunt inwhich the metal cap is attached to the plastic shell and the primersealing ring is pushed into shape.

FIG. 18 is a cross-sectional view of the main or final hunt in which themetal-capped plastic shell is formed to final dimensions.

Referring now to the drawings, FIG. 1 shows a shotgun shell casinghaving a tubular body portion 12 which may be skived to form a taperedend 14 at its mouth end and which has an integrally formed transversebase portion 16 at the breech end of the shell. The tubular body portion12 is essentially of uniform wall thickness although the rear portion 18tapers slightly near the base portion. A conventional metal head member20, of brass, steel, or any other suitable metal, is attached to thebase portion 16 primarily by an annular rim 22 integral with the baseportion 16 and by the annular metal skirt 24 which projects inwardlyinto the primer opening 26 of the base portion. Integral with the baseportion 16 is a continuous gas sealing skirt 28 which projects inwardlytowards the center of the opening to form an annular ring having a borewhich is less than the primer bore. An alternative method of attachingthe metal cap to the plastic base portion is to provide a plurality ofprongs (not shown) in place of the annular metal skirt 24 and embed theprongs in the plastic base portion.

A primer 30 is inserted by force fit into the primer bore and extendspast the forward end of the primer sealing skirt 28 so that the skirtforms a continuous surface with the cylindrical wall surface 26A of theprimer bore. (See FIG. 2A) It can be seen that the gas sealing skirtdoes not come into direct contact with the combustion heat and gaseswhich result from the ignition of the propellant means. Thus, it can beexpected that there will be less erosion of the primer seal as a resultof the hot combustion gases.

The gas sealing skirt 28 utilizes a collar of plastic drawn out to anoriented section and buttresses with a tight fitting primer bore toconcentrate stresses across a thin band or line of contact betweenplastic and primer.

It should be recognized that the working or shaping of manythermoplastics, and especially polyethylene, is an art as contrasted tothe working of metals. In the case of polyethylene, the pieces ofplastic shaped by tools bear little resemblance in profile and dimensionto the tools that did the shaping. These tools must be so shaped tocompensate for the high degree of dimensional recovery that is typicalof polyethylene after a severe cold-forming operation. In general, anyplastic that can be mechanically deformed below its melting point can beprocessed according to the present process.

The starting point of the process is to provide a tubular plastic slug32. (See FIG. 3) This plastic slug can be made in various ways but fromthe standpoint-of economy, it has been found that extruded plasticheavywalled tubuing, cut to proper length, can be used very convenientlyand economically.

The process which has been developed involves the utilization ofoperating die sets of the progressive trans-. fer type so that the timeinterval between steps is measured in fractions of a second. For thisreason, the configurations and shapes of the workpieces shown in theFIGS. 4 through 7 are not entirely correct since the plastic afterdeformation takes some time to recover to the dimensions shown in theFIGURES. It is impossible to accurately measure the shape of the plasticimmediately after removal from the dies since the plastic is in theprocess of elastic recovery and change due to this memory. The FIGURESthus represent sketches of workpieces which have been withdrawn from theprocess at that particular point and allowed to cool and attain a stablevalue.

The processing described in the following text can be accomplished onslugs at ambient temperature. Although a single-action press withauxiliary motions for powering transfer "bars and undermotion knockoutsleeves was used for most of the development work, the productionpresses can be relatively high speed and large enough to handle multiplerows of tools.

Slugs 32 are fed to each row of tools end .to end (not shown) and arepositioned over the first mechanical working station called preform.There are two tools used in this station, a top punch 34 and a supportdie 36. (See FIG. 9)

An important function of the preform step is to stretch the slugradially and prepare it to fit accurately into the die bore of the nextprocessing step (impact extrude). Since plastic has a large elasticrecovery and a memory factor, it is necessary to select tool diametersof punch 34 so that the slug is overstretched. The uppermost portion 34aof punch 34 establishes a top flare on the preform to add a safetyfactor for punch entrance in the next operation.

FIG. 9 shows tool positions at the bottom of the machine stroke. On theupstroke, the preform is lifted up and is stripped against a stationarybushing (not shown).

The preform is then moved into axial alignment for the next operationcalled impact extrude. (See FIG. 10) Impact extrude is a severemechanical operation and requires the greatest thrust of any of thesteps in the process.

There are two tools used in this step, a die 40 and an extrusion punch42. Punch 42 has a series of important dimensions and profiles.Beginning at the lower extremity, it has a taper section 42a, then astraight cylindrical section 42b, an enlarged knob-shaped working punchland 42c, and finally the support shank 42d of the punch.

Tapered section 42a enters the bore of preform 38 and expands itradially into contact with the extrusion die bore 40a. Preform 38 can beat room temperature or at an elevated temperature below the crystallinemelt temperature for the plastic being used. The diameter of cylindricalsection 42b of the punch and the bore 40a are so related that thepreform does not Eckstein or buckle when the working punch land 42cbegins the actual impact extrusion of the plastic. The diameter ofworking punch land 42c is selected to clear the die bore 40a by anamount which will produce the desired wall thickness in the body of thefinished shell. However, because of the elastic recovery of the plastic,the actual clearance between the punch and die is much less than theshell wall thickness produced.

The support shank 42d of the punch is back tapered to minimize the areaof shell in contact with the punch at the instant of extrusion since thethick collar at the top of the extrusion (which becomes the base of theshell) contracts very rapidly. The extrusion die 40 includes a flaredmouth 40b which is critical in establishing the wall thickness gradientbetween the tubular body section and the head portion of the finishedshell. The amount of energy liberated at each 6 stroke is enough torequire water cooling of punch 42. This may be accomplished by anywell-known means.

It can be seen from FIG. 5 and FIG. 10 that the plasticj workpiece hasbeen substantially elongated in the axial or longitudinal direction andthat an impactextruded component .44 has been formed which has asubstantially straight walled tubular body portion 44a and a thickwalled rear end section 44b, which thick wall is on the exterior of thebody member. The forward end44c, shown between punch land 42c and dieinsert 40c, is important to keep the tools from striking each other.

The next operation performed on the shell is to trim the excessportion-44c from the forward or mouth end of the shell. This can be doneby lancing with a knife or by any other well-known means. FIG. 11 showsthe portion 440 detached from the component after the component has beenmoved past the lancing means 45. After the removal of the portion 44c,the shell mouth of the trimmed component 46 is at complete open bore andcan be supported with a full diameter stem within the next station whichis called profile inversion. V Profile inversion is a gathering orinversion of plastic which has been positioned on the exterior of theworkpiece at its upper end. This operation serves to crudely form theshell head and prepare it for final forging. This operation uses twobasic tools, a hunter 48 and a stem 50. (See FIG. 12).

Stem 50 has a precision profiled nose 50a and is in serted in thetrimmed impact extruded component 46 to support the shell whileshroud-like bunter 48, with itsprofiled bore, establishes the requiredbore and diameter of the head section in the component. In opera tion,the trimmed impact extrusion 46 is located in axial alignment with stem50. The bunter 48 descends and drives the workpiece over the stem andeffects a diameter reduction of the component top. At some instant inthe stroke, the clearance between stem 50 and the bore of bunter 48serves to lock and support the component for further compression andinward folding. Thecomponent 52 is then removed from the stem 50 andmoved to the next station called pre-heading. (See FIG. 13)

It is the purpose of pre-heading to complete the dimensional and profilerequirements for the head of the shell.

The pre-head station utilizes three main tools to support: and forge theplastic workpiece or component, Le, a hunter 54, a stem 56, and a diemeans 58. The component 52 is supported by a stem 56 and a die 58 and iscompressed by a bunter 54 which has a complex series of contours to formthe preheaded component 60..Tl1e counterbore 54a fashions the extrudedcollar 60d and the corner cutaway 54b produces the rim 60b. Extrudedcollar 60a surrounds the primer bore and subsequently will be deformedto become the primer gasiseal. Rim 60b will be reformed to become therim fill of the cap which is added in a later step of the process.

In operation, the profile inversion component 52 is driven by the hunter54 into the die 58 as well as over the stem 56. Preheading is ahigh-thrust operation in which plastic flows and extrudes into all freespace that is vented. This flow makes it possible to form the collar 60aand the rim 60b. The flow also verifies the tapered wall between thehead and body sections of the shell.

FIG. 13 shows the tool position at the bottom of the stroke. Again thecomponent is lifted from stem 56 and die 58 on the upstroke, preferablyby means of a knockout sleeve (not shown).

The pre-headed component 60 is then transferred into axial alignmentwith the last station in the progressive die set. It is a simple sizingoperation. (See FIG. 14) There are two tools used, a die 64 and a punch66. In operation, the pre-headed component 60 is pushed mouth downthrough the die 64. The position of the tools shown in FIGVM is amid-point in the downstroke of the press.

The sizing operation serves as a corrective means, attained withinexpensive tooling, for establishing a desired body diameter on thefinished shell.

After mechanical processing, the sized components 62 are washed free oflubricant and simultaneously stabilized dimensionally by using a hotwater wash. The temperature of the wash is selected to coincide with themaximum temperature expected in storage conditions for the finishedshells. Higher temperatures at wash accomplish dimensional stability inshorter times. For this purpose, 170? F for 20 minutes is suitable.

Components thus washed and stabilized are ready for the assembly withmetallic caps and primers. Basically, the equipment includes a stem 68and a die 70. (See FIGS. 15-18) In practice, the support stem 68 ispositioned to hold the component well above the heading die 70 for thefirst working station (FIG. 15) of this series. A shroud-like bunter 72with center punch 74 inverts the collar 60a (FIG. 7) into position 76and the rim 60b (FIG. 7) is tapered inwardly for ease in applying themetal cap 20 in the following work station.

FIG. 16 shows the cap 20 in place. The cap 20 has been half headed,i.e., the preparation for the primer and the rim bulge 78 made in aseparate operation. A simple flat end punch 80 is used for seating thecap.

FIG. 17 shows the stem 68 dropped to align the capped shell within thedie 70 at matching position of die shoulder 70a with cap bulge 78.Bunter 82 with center punch 84 drives the shell into location. Theinverted collar 76 is drawn out into a thinner section and the rimmaterial 60b is displaced into the cap bulge 78.

FIG. 18 shows the finishing bunting of the shell. Bunter 86 with centerpin 88 is critically profiled to provide finished dimensions to the gassealing collar and the primer bore. Also at this station, the metallicrim of the cap 20 is compressed to hold onto the plastic fill that hasbeen prepared in the previous station (FIG. 17). The top area on the capwhich will receive the flange of the battery-cup type primer is alsoverified at this station.

In all of FIGS. 15-18, the punches and bunters are shown at the bottomof the press stroke.

Priming the shell may be done by the conventional method of insertingand seating of a regulation batterycup type of shotshell primer. Thelocation of the gas sealing collar 28 is such that it will function witha shorter battery cup usually found in European made shotshells or withlonger battery-cup primers generally used in the United States.

Because of elastic recovery and memory," the extruding of plasticbetween a punch and die does not result in a plastic article having theshape and dimensions of the space between the punch and die.

A substantial amount of deformation and movement of plastic is necessaryto achieve the desired results in the present invention. For example, aslug as shown in FIG. 3 having an CD. of 0.665 inch and an I. D. of0.230 inch is expanded at the base end 44b in FIG. 5 in the impactextrude step to an O. D. of 0.912 inch and an I. D. of 0.495 inch andfinally forged, sized, etc. to a finished shell having a base 0. D. of0.790 inch and a primer bore of 0.220 inch.

The impact extruded dimensions listed above are the cooled dimensionsand are not the dimensions of the plastic workpieces at the time theyare subjected to deformation in the die set. Accordingly, the tooldimensions are somewhat greater than those listed for the plastic sincethe plastic workpieces must be expanded before elastic recovery andmemory takes over. However, the dimensions are relatively accurate sothat some indication can be gained as to the amount of radialdeformation of the plastic slug.

It can also be seen name elongated, thickened endwall portion 44b (FIG.5) is deformed substantially in order to finish as the base portion 16of the final shell (FIG. 1). Thus, there are specific portions of thebase portion 16 which are at least moderately oriented or deformed,e.g., primer seal ring 28 and annular n'm 22. Other sections of the baseportion, because of the substantial cold working of the plastic toachieve the shape and dimensions of the final shell, can be expected tobe oriented and strengthened to some degree. The tubular body wallportion 12, of course, is highly oriented in a longitudinal as well as acircumferential direction.

1. A cartridge casing made of thermoplastic material having a tubularbody portion and an integrally formed base section, a primer openingextending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttressedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising a continuous, annular skirt meansformed integrally with said base section to project inwardly towards theFem e1 line of said primer opening when said primer is not in place andwhich is forced back against said base section to form a continuoussurface with said cylindrical wall means when the primer means is inplace.

2. A cartridge casing made of thermoplastic material having a tubularbody portion and an integrally formed base section, a primer openingextending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttressedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising an annular skirt means integrallyformed at its rear end to said base section and having its forward, freeend projecting inwardly toward the center line of said primer openingthus forming a continuous groove means between the forward end of saidskirt means and said cylindrical wall means.

3. A cartridge casing as recited in claim 2 in which said annular skirtmeans is so positioned that the forward end of the primer means, when inplace, extends past the forward, free end of said skirt means so thatthe entire skirt means is forced between the primer means and the basesection of the cartridge.

4. A cartridge casing made of thermoplastic material having a tubularbody portion and an integrally formed base section, a primer openingextending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttressedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising a continuous, annular skirt meansintegrally formed with said base section and whose plastic material hasbeen substantially deformed and whose crystalline structure is at leastmoderately oriented.

mg? UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No.3,786,755 Dated January '22, 1974 I flQGEORGE R. ECKSTEIN and WILLIAM G.MOYHER It is certified that error appears in the above-identified patentand that said Letters Patent are-hereby corrected as shown below:

Abstract; Page, ;-oppos:|.te the heading Inventors, "George R. EcksteinWilliam G. Moyher, both of Fairfield, Conn." should read as George R.'Eckstein', Fairfield; William G. A Moyher, Stratford; both of Conn.'-.Col. 1, Lines 50-51, "Ecks'ten'? should read as 'Eckstein'--.'

. Col. 3-,- Line 60,- :"tubu-ing" should" read as -'-tubing-'.

Col. 4, Line 54 "Eckstein" should read as -wrink,le.

, Signedandsealed t his 9t h day brqul 'wn.

(SEAL)- MCCOY D I GIBSON,.*JR 4' v c. MARsI IAL DANN Attesting Officer"p Commissloner of Patents mg UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,786,755 Dated Jariuary 22, 1974Ihventfi-(QGEORGEiR. ECKSTEIN and WILLIAM G. MOYHER It is certified thaterror appears in the above-identified patent and that said LettersPatent are-hereby corrected as shown below:

Abstract Page,- opposite the heading Inventor's, "George R. V Ecksteihz.William G. Moyher both of Fairfield, Conn." should read as "George R.'Ecksiiein, Fai'rfield; William G. Mo'yher, Stratford; both .013'Conn'.-f.' m a 4 Col; 1, 'Lines 50-51, "Ecks'ten'! .s'ho'uld 're ad'as--'Eckstein-'-; Col. 3 Line 60,: "tubuing" should read as --tubing-'--.

(201.2 4, Line 54 "Eckstein'W should read as -'-wrinkle--.-.

, Signed and; sealed this 91' i y 6f JI'ilY (SEAL) MCCOY I M {1GIBSONQQIY-JRQ 7 a c. MI ARSI I'ALL D N, Attesting Officer" YCommlssionerof Patents

1. A cartridge casing made of thermoplastic material having a tubularbody portion and an integrally formed base section, a primer openingextending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttrEssedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising a continuous, annular skirt meansformed integrally with said base section to project inwardly towards thecenter line of said primer opening when said primer is not in place andwhich is forced back against said base section to form a continuoussurface with said cylindrical wall means when the primer means is inplace.
 2. A cartridge casing made of thermoplastic material having atubular body portion and an integrally formed base section, a primeropening extending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttressedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising an annular skirt means integrallyformed at its rear end to said base section and having its forward, freeend projecting inwardly toward the center line of said primer openingthus forming a continuous groove means between the forward end of saidskirt means and said cylindrical wall means.
 3. A cartridge casing asrecited in claim 2 in which said annular skirt means is so positionedthat the forward end of the primer means, when in place, extends pastthe forward, free end of said skirt means so that the entire skirt meansis forced between the primer means and the base section of thecartridge.
 4. A cartridge casing made of thermoplastic material having atubular body portion and an integrally formed base section, a primeropening extending longitudinally through said base section, primer meanspositioned in said primer opening in close fitting relationshiptherewith, said opening being defined by a substantially cylindricalwall means which extends through said base section, and a gas sealingmeans located in said primer opening intermediate the ends thereof, saidsealing means comprising an elongated seal which is buttressedsubstantially along its entire length by the base section of thecartridge casing when the primer is inserted into the primer opening,said gas sealing means comprising a continuous, annular skirt meansintegrally formed with said base section and whose plastic material hasbeen substantially deformed and whose crystalline structure is at leastmoderately oriented.